<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
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<body>
    <script>
        //1  for 循环--循环次数已知  循环次数未知---while do-while
        var sum = 0;
        for(var a=1;a< 101;a++){
            sum += a;
        }
        console.log(sum);

    </script>
</body>
</html>
